Rydberg electron transfer to C6H5NO2: Lifetimes and characteristics of the product C6H5NO2- ions

The nature of electron binding in C6H5NO2- ions produced by Rydberg electron transfer in K(np)/C6H5NO2 collisions is investigated through measurements of the number and the lifetimes of the product ions and their dependence on Rydberg atom velocity and principal quantum number n in the range 12 < or approx. n < or approx. 30. The data are interpreted by comparison to results obtained using well-known dipole-bound and valence-bound anions. At high n direct capture into valence-bound states with a lifetime of ∼1.6 ms is observed. At low n the data suggest that, while direct capture into valence-bound states is still possible, the majority of the observed C6H5NO2- ions result from the onset of a second reaction channel that involves the formation of a dipole-bound 'doorway' state that rapidly evolves into a state with predominantly valence-bound character. These findings are discussed in the light of earlier work on electron binding to C6H5NO2